sedimentary
Chert (Flint)
Microcrystalline Quartz (SiO2)
Hardness: 7 (Mohs scale), Color: Brown, gray, or tan with a waxy luster. Conchoidal (shell-like) fracture. Generally opaque to translucent.
- Color
- Brown, gray, or tan with a waxy luster
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Physical properties
Hardness: 7 (Mohs scale), Color: Brown, gray, or tan with a waxy luster. Conchoidal (shell-like) fracture. Generally opaque to translucent.
Formation & geological history
Formed by the accumulation of silica-rich organic remains or chemical precipitation in marine environments. Often found as nodules in limestone or chalk beds.
Uses & applications
Historically used for making sharp stone tools (arrows, knives). Currently used in road construction, landscaping, and flintlocks for firearms.
Geological facts
Flint was used by early humans for millions of years to create sparks for fire and sharp edges for tools. It produces a very clean, sharp edge when struck.
Field identification & locations
Identified by its extremely sharp edges when broken and characteristic curved fracture patterns. Found globally in sedimentary basins. Look for a white chalky outer 'cortex' if unweathered.
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